This invention relates to a method and apparatus for detecting a roll-over condition of a vehicle by analyzing forces acting on the vehicle.
Commercial trucks are an extremely popular way to transport freight, since it is versatile and inexpensive compared to other modes of transportation. Commercial trucks typically include a cab which hauls one or more cargo trailers. One safety issue relating to these types of trucks is the risk of roll-over of the vehicle which places the safety of the driver of the truck and of other adjacent vehicles at risk.
A roll-over condition typically occurs because a vehicle takes a turn at excessive speed or loses traction along the turn. The roll-over generally begins at the rear trailer of the vehicle as the rearmost wheels begin to tilt relative to the road surface. Unfortunately, by the time this effect progresses to the cab of the vehicle and is noticeable to the driver, the tilt of the rear trailer has drastically increased. At this point, it is usually too late to take corrective measures such as slowing the vehicle to prevent the roll-over from taking place.
One method to detect a roll-over condition is to mount a single accelerometer on the vehicle to measure the gravitational forces acting on the vehicle. Accelerometers measure forces in a single direction, and the accelerometer is mounted on the vehicle to measure the full force of gravity when the vehicle is upright. As the vehicle begins to tip, the readings from the accelerometer will decrease because the gravitational forces are no longer acting in the same direction relative to the accelerometer. When the measurements from the accelerometer decrease below a threshold value, a warning signal can be actuated to alert the driver of a roll-over condition.
The method described above has several disadvantages. First of all, during operation of the vehicle the readings from the accelerometer will fluctuate due to bumps and other variations in the road surface. To compensate for this, the measurements must be averaged over time. If the measurements are averaged over a short period of time, a false positive reading could occur if several low readings from the accelerometer are coincidentally taken in a row. If the measurements are averaged over a long period of time, the system may not respond quickly enough to give the driver adequate time to stabilize the vehicle.
Finally, the readings from an accelerometer will vary depending upon the weight of the vehicle, the air temperature surrounding the accelerometer, and other factors. As discussed above, the readings from the accelerometer are compared to a threshold value to determine whether a roll-over is occurring. However, in order for the system to work, the threshold value would have to be altered as the payload of the vehicle changed, as the outside temperature changed, and as any other relevant factor changed.